Not Applicable
Not Applicable
The present invention relates in general to electrical/electronic weighing systems and more particularly to strain gauge load cells used on forklift trucks.
It is known that, in addition to typical lifting and transporting functions performed with forklift trucks and the like, weighing functions can also be carried out with this type of equipment when fitted with a weight measuring system. Various such systems have received patents and are being used. However, specific problems can and do arise with prior art systems with regard to carrying out lifting and weighing operations, manufacturing costs, installation and servicing.
Some systems require structural modifications or additional attachments to the lift truck, adding cost and resulting in more difficult and time consuming installation as evident in U.S. Pat""s to Weigh-Tronix, U.S. Pat. Nos. 4,421,186 and 6,002,090.
Some systems are limited in ease of performing weighing functions in that they must be activated into the lift mode before weighing functions can be performed as evident in U.S. Pat. to Zefira, U.S. Pat. No. 5,739,478.
Some systems employ technically and physically elaborate approaches to address excessive vertical forces, lateral forces and binding in the weighing system that can cause inaccurate weight readings and damage to the load cells as evident in U.S. Pat""s to Weigh-Tronix, U.S. Pat. Nos. 4,421,186 and 6,002,090.
Some systems use only a portion of the lifting surface for weighing, limiting load placement options, and employ partial shrouds or covers that do not extend over the entire fork and subassembly surface and will be prone to allowing foreign substances such as dirt and water that could cause false readings from the weigh system as evident in U.S. Pat. to Russo, U.S. Pat. No. 4,420,053.
Some systems employ mechanically elaborate designs, likely to be prone to mechanical malfunction and high manufacturing cost, to address weight measurement accuracy problems resulting from eccentric loads as evident in U.S. Pat. to Baldwin, U.S. Pat. No. 4,368,876.
Some system designs are not based on standard lift truck fork configurations and are thicker or higher in cross section or have component details that protrude above the general height of the fork lifting surface making it more difficult or impossible to slide the forks under a standard pallet as evident in U.S. Pat""s to Boubille, U.S. Pat. No. 4,899,840 and S""More, Inc., U.S. Pat. No. 5,861,580. Further, systems not based on standard lift truck forks tend to require more custom manufactured components and complexity, usually resulting in higher manufacturing costs and requiring more highly skilled or knowledgeable service personnel respectively.
Some systems require additional weigh system attachment components such as a secondary carriage that can create a potentially unbalanced and unsafe condition because the position of the forks is moved forward relative to the lift truck resulting in incorrect load centers specified by the lift truck manufacturer as evident in U.S. Pat""s to Weigh-Tronix, U.S. Pat. Nos. 4,421,186 and 6,002,090.
Some systems do not allow weighing functions to be performed with the lifting surface in the fully lowered position making it difficult or impossible to safely check load weight relative to the maximum lifting capacity of the lift truck before attempting to lift the load as evident in U.S. Pat. to Zefira, U.S. Pat. No. 5,739,478.
A weighing apparatus, in particular weigh sensed lift truck forks for which the design is generally based on a standard lift truck fork. These forks are each modified to accept an assembly of load sensing cells and their wiring, spacers, fasteners, reinforcing ribs and cover. Each cover provides load cell protection, standard fork tip functionality, a load bearing surface and a structure that interfaces through spacers with the load cells to provide load weight readings to an operator. Each fork cover is affixed through spacers to the load cells which are in turn affixed through spacers to each fork. The tip section from each standard fork is cut off, modified and welded flush to the front end of each fork cover, providing functionality for normal lift truck operations.
As various approaches in prior art address certain problems but not others, it is a prime objective of this invention to more fully address the range of problems that relate to the application of this type of equipment, within the scope of this invention.
A feature of this invention is the use of standard lift truck forks that minimize custom manufactured components and reduce manufacturing costs.
Another feature of this invention is that because standard forks are employed, modifications to the lift truck or additional attachment components are not required making installation easier. Further, the standard nature and simplicity of design allow servicing by regular technicians without highly specialized knowledge and the option of servicing onsite.
Another feature of this invention is that it provides protection to load cells against vertical and lateral overloading and accomplishes this through simple component spacing, fastener tensioning and with only a few basic components.
Another feature of this invention is that weighing functions can be performed with the forks in the fully lowered position and as a result, load weight can be safely checked relative to the maximum lifting capacity of the lift truck before attempting to lift the load thus avoiding potential injury to the operator and damage to the lift truck.
Another feature of this invention is that because additional attachment components such as a secondary carriage for mounting the forks are not required, the position of the forks is kept safely at the distance from the lift truck specified by the manufacturer, thus maintaining proper balance between the forks and the truck for lifting and weighing functions.
Another feature of this invention is that the low profile and uniform top surface of the forks allow easy access to standard pallets.
Another feature of this invention is that the load cells are electronically matched to give accurate weight data regardless of the positioning of a load on the forks.
Another feature of this invention is that the cover completely surrounding the top and sides of the fork and load cell subassembly, minimizing contamination by foreign substances and shielding the subassemblies from direct impact.